Effect of Bubble Coalescence on Material Removal Rate in Electrical Discharge Machining Process

This paper investigates the ease of bubble coalescence of the machining liquid and the medium at the discharge ignition location in electrical discharge machining (EDM) process in order to discuss the effect of the properties of the machining liquid on the material removal rate. Bubble coalescence, which is one of the properties of a machining liquid, was observed using a video camera, and the medium at the discharge ignition location, i.e., whether a discharge occurs in EDM oil or in bubbles, was determined using a characteristic of the waveform of the discharge current. It is found for a continuous EDM process that a high proportion of discharges occur near the boundaries of previously existing bubbles, whereas few discharges occur in the interior of bubbles. It is also found that reducing the bubble coalescence will improve the material removal rate.